FiveSeveN magazine issue-- non drop free mags

My Channel: http://www.youtube.com/user/BuffmanLT1

Seems as if the Promag (well they're junk anyways and don't count) doesn't drop free, and neither do two of the factory FN mags I have that don't have the metal showing on the back of the mag. The first one you see in the video wouldn't drop free, but apparently it does now. It was the same as the one that doesn't. If you look at the pictures at the end you can see a rough casting line inside the magwell. Should I sand those down?

This all started after removing the magazine safety disconnect. I have no issues reinstalling if it solves the problem.